This invention relates to manufacture of magnetic recoding disks. Especially, this invention relates to a step of removing protrusions on a substrate and a step of forming a lubricant film on the substrate.
The manufacture of a magnetic recording disk such as a hard disk is roughly divided into former steps and latter steps. The former steps include deposition of an underlying film, deposition of a magnetic film for a recording layer, and deposition of an overcoat. The latter steps include preparation of a lubricant layer and other required steps. The lubricant layer is prepared considering contact of a magnetic head onto the disk in read-out.
The preparation of the lubricant layer is carried out by a following procedure.
To begin with, a substrate is taken out to the atmosphere after deposition steps because thin-films such as the magnetic film for a recording layer are usually deposited in a vacuum chamber. Then, burnishing is carried out to remove contaminants adhering to the substrate and to remove protrusions formed on the substrate during the film depositions. The burnishing is the step of removing the protrusions and the contaminants from the substrate by rubbing it with a tape-shaped polishing member. xe2x80x9cContaminantxe2x80x9d in this specification means material that may contaminate a substrate in general, which is gas, ion, molecular, particle or another substance.
The lubricant layer is prepared after the burnishing. As lubricant, a fluorine lubricant such as perfluoropolyether (PFPE) is used. Such the lubricant is diluted with solvent for improving uniformity. The diluted lubricant is coated onto the substrate by such a method as the dipping method where the substrate is dipped into the stored lubricant, or the spin-coating method where the lubricant is dropped onto the substrate when it is spun.
xe2x80x9cSubstratexe2x80x9d means a board that consists a magnetic recording disk in this specification. xe2x80x9cSurface of substratexe2x80x9d may mean a surface of a film or layer when a film deposition or a layer preparation has already been carried out onto the substrate.
Recent improvement of recording density in magnetic recording disks is remarkable. For example, in hard disks it is becoming 20 gigabit/inch2 in the year 2000 and 40 gigabit/inch2 in the year 2001. One of factors that enable the improvement of the recording density is to reduce the spacing. FIG. 19 shows a view explaining the spacing.
In FIG. 19, the spacing in case of hard disks is explained as an example. As shown in FIG. 19, a hard disk has the structure where a recording layer 91 is prepared on a substrates 9, an overcoat 92 is deposited on the recording layer 91, and a lubricant layer 93 prepared on the overcoat 92. A magnetic head for write and readout of information is located at a position slightly apart from the surface of the hard disk. The spacing, which is designated by xe2x80x9cSxe2x80x9d in FIG. 19, means distance between the write-readout device element 900 of the magnetic head and the recording layer 91 of the hard disk. Distance between the write-readout device element 900 and the lubricant layer 93 is called xe2x80x9cflying heightxe2x80x9d, which is designated by xe2x80x9cFHxe2x80x9d in FIG. 19. It is important to make the spacing S small in improving the recording density.
As the spacing S becomes smaller, demands to the manufacturing process have been becoming severer by years. For reducing the spacing S, it is required not only to reduce the flying height FH, which is about 10 to 20 nm in a typical hard disk drive (HDD) currently on sale in the market, but also required to make thickness of the overcoat 92 and thickness of the lubricant layer 93 thinner. As thickness of the overcoat 92 is made thinner, it is required to deposit a more compact and harder film as the overcoat 92. As thickness of overcoat 92 is made thinner, demand for thickness uniformity of the lubricant layer 93 becomes severer as well as demand for enhancing adhesion strength of the lubricant layer 93 becomes severer.
With the above described points in the background, method for depositing the overcoat 9 has been shifting from the conventional sputtering method to the chemical vapor deposition (CVD) method. Usually a carbon film is deposited as the overcoat 92. By the CVD method, it is enabled to deposit a carbon film called xe2x80x9cdiamond-like carbonxe2x80x9d (DLC) film. DLC film is known as the hard, compact and stable carbon film even when its thickness is small. This is the reason why the method has been shifting to the CVD method.
However, contaminants of gases or ions may adhere to the overcoat 92 under influence of residual gases when it is deposited by the CVD method. In addition, minute protrusions are easily formed on the overcoat 92 in the CVD method, resulting from abnormal film growth. If the lubricant layer 93 is prepared over the overcoat 92 on which contaminants or protrusions exist, there easily arise problems such as adhesion strength of the lubricant layer 93 may decrease, and thickness of the lubricant layer 93 may lose uniformity.
Adhesion strength of the lubricant layer 93 is enhanced when terminal groups of macromolecules composing the lubricant are bonded sufficiently with a carbon of the overcoat 92. For making adhesion strength higher, it is preferable that the macromolecules are bonded with a carbon in the surface of the overcoat 92 at one of or both terminal groups. On the other hand, it is desirable that degree of freedom of the macromolecules is high at the portion adjacent to the surface of the lubricant layer 93, on purpose of prevention the write-readout device element 900 of the magnetic head from chucking with the disk. In short, both terminal groups are preferably not bonded.
Macromolecule bonded with a carbon at one of or both terminal groups is hereinafter called xe2x80x9cbonded lubxe2x80x9d. Macromolecule not bonded with a carbon at either of terminal groups is hereinafter called xe2x80x9cfree lubxe2x80x9d. Thickness ratio of the bonded lub layer against the whole lubricant layer 93 is hereinafter called xe2x80x9cbonded ratioxe2x80x9d. Though the optimum bonded ratio has been supposed about 20-30% so far, demand for accuracy of the bonded ratio tends to be severer as the lubricant layer 93 is made thinner.
For obtaining the demanded bonded ratio, it has been attempted to carry out treatment for controlling bonds of the terminal groups after the lubricant-layer preparation. In this treatment, thermal energy or light energy is applied to the lubricant layer 93, thereby controlling bonds of the terminal groups. This treatment is hereinafter called xe2x80x9cpost-preparation treatmentxe2x80x9d.
However, when the overcoat 92 is exposed to the atmosphere after the deposition, many contaminants of gases or ions in the atmosphere are adsorbed with the surface the overcoat 92 because the surface has been chemically activated. As a result, when the lubricant layer 93 is prepared, a contamination layer may be formed between the lubricant layer 93 and the overcoat 92. If the contamination layer is formed, it may become difficult to obtain an accurate bonded ratio by the post-preparation treatment. For preventing these problems, equipment that reduces contaminants is required. Including such the point, the current situation is that huge investment is inevitable for coordinating manufacture environment.
Object of the invention is to solve the described problems in the manufacturing process, which have been brought from the reduction of the sp acing.
To accomplish this object, the invention presents a method and an apparatus for manufacturing a magnetic recording disk, where steps from magnetic-film deposition to lubricant-layer preparation are carried out without vacuum breaking. The invention also presents a method and an apparatus for manufacturing a magnetic recording disk, where a substrate is cleaned prior to lubricant-layer preparation. The invention also presents a method and an apparatus for manufacturing a magnetic recording disk, where burnishing is carried out in vacuum after magnetic-film deposition. The invention also presents a method and an apparatus for manufacturing a magnetic recording disk, where post-preparation treatment to coordinate adhesive strength and surface lubricity of a lubricant layer is carried out in vacuum. The invention also presents an in-line type substrate processing apparatus comprising a plurality of vacuum chambers provided along each of a plurality of circumventive transfer paths, a connection transfer path connecting at least two of the circumventive transfer paths, and a transfer system that transfers a substrate to be processed along the circumventive transfer paths and the connection transfer path without exposing the substrate to the atmosphere.